As a device for measuring an inner diameter of a hollow member, a non-contact type inner diameter measuring device is known, which projects a laser beam over total circumference, forms an optical ring on inner surface, takes an image of an optical ring thus formed, and measures inner diameter, shape, and profile of the hollow member on the image. Also, an inner diameter measuring device is known, which brings contact to inner surface of the hollow member with a contact, and measures the inner diameter.
As a non-contact type inner diameter measuring device, the devices disclosed in the Patent Document 1 and the Patent Document 2 are known. According to each of the Patent Document 1 and the Patent Document 2 discloses a non-contact type inner diameter measuring device, a laser beam is projected over total circumference, an optical ring formed on inner surface of a cylindrical object is photographed and shape and diameter of the optical ring is measured on the image.
Further, as a contact type inner diameter measuring device, a device disclosed in the Patent Document 3 is known. According to the Patent Document 3, a pipe no be inspected is rotatably supported by a pipe rotation supporting device, and the device comprises a running carriage device where a pair of upper and lower inner diameter measuring sensors are provided in closely separable manner. By operating the running carriage device, the inner diameter measurement sensor is inserted into the inside of the pipe to be inspected. By separating the inner diameter measuring sensor in upper and lower directions, the sensor is brought into contact with inner surface of the pipe to be inspected. Further, the pipe to be inspected is rotated by the pipe rotation supporting device, and inner diameter of the pipe to be inspected is measured.
By the non-contact type inner diameter measuring device in the former case, a shape and a condition of the inner surface can be quickly identified, and it is advantageous in that the measurement can be carried out within shorter time, and the conditions of inner surface such as graded step, taper, etc. at one time, and entire shape and condition can be identified, while there is a problem that the measurement with high accuracy cannot perform.
By the contact type inner diameter measuring device in the latter case, the measurement results with high accuracy can be obtained, while measurement must be performed one by one and much time is required. Further, measurement must be performed at a multiple of points for measuring a shape of inner surface, and a long time is required for the measurement. Also, there are problems in that it is difficult to identify the conditions of inner surface such as graded step, taper, etc.
To solve the problems as described above, it is an object of the present invention to provide an inner diameter measuring device, by which it is possible to quickly identify the conditions of the inner surface and entire shape, and moreover, to obtain the measurement results with higher accuracy.